To date, surgery has been performed with instruments using inorganic materials (mineral- and metal-based) and physical effects to function. Initially the scalpel was used solely to make incisions in tissue. The composition of these scalpels has historically followed the trend of blades composed of flint, bronze, iron, and finally stainless steel. Current scalpels use inert materials such as stainless steel to cut tissue, or use energy from electrical, laser, or ultrasonic fields to simultaneously cut and cauterize the tissue. The steel scalpel has the disadvantage of bleeding from the incision, whereas cauterization methods destroy tissue to mitigate bleeding. Likewise, other current medical devices and implants use inert materials.
Limiting blood loss during surgery is a universal patient need that is essential for maintaining normal perioperative tissue and organ function and optimizing post-operative recovery. Consequently, the scalpel was reconfigured to simultaneously cut tissue and reduce bleeding. Some scalpels use heat to cut and cauterize tissue, and thus induce protein denaturation, which leads to fusion of intimal layers of blood vessels. Such scalpels employ physical fields such as electrical (ohmic heating), magnetic, electromagnetic, laser (light absorption), or ultrasonic (thermoviscous effects). Heat scalpels also include electrosurgery, harmonics, and CO2 lasers. Each of these heating techniques causes thermal denaturation of blood proteins that are known to enhance hemostasis but also damage tissue and nerves.
Electrosurgery heats the scalpel blade by direct or alternating current passing through a resistive metal wire electrode into the patient's body and back to the generator though a receiving electrode adhesive pad. The pad is typically applied to the distal portion of the patient's leg. Electrosurgery can result in an unintended burn if the electrical current leaks to any conductive element, or if the electrode cable comes in contact with the patient's body. At lower frequencies, the electrical current can also depolarize cell membranes, and can cause neuromuscular excitation, pain, and even cardiac arrhythmia. However, at high frequencies, the current is less able to affect ions within the tissue cells, making neuromuscular effects negligible. In comparison to other methods, tissue heating from electrosurgery is more localized, which may reduce adverse effects on the tissue.
In the last 20 years the design of CO2 lasers has improved due to the introduction of a new hollow tube delivery system that is currently favored for its limited damage of adjacent tissue. In comparison to harmonic scalpels, which use mechanical ultrasonic vibrations to coagulate blood and cauterize tissue, CO2 lasers can cauterize vessels as small as 0.5 mm in diameter. CO2 lasers and electrosurgery devices may perform with statistically significant speed, on incision and excision, compared to traditional cold knife scalpels and additionally produce less tissue damage. However, scientists disagree on which scalpel is less damaging to tissue and nerves. Some studies have shown that electrosurgery and harmonic scalpels are equally damaging to nerves. Results were based on incisions at three different distances from the nerve: 1 mm, 3 mm, and 5 mm. When tissue was cut adjacent to a nerve, the closer to the nerve, the more nerve damage occurred. However, according to these results, the differences between these devices are negligible. They all burn tissue. High temperatures cause rapid explosive vaporization of water content within tissue, causing fragmentation and drying. Heat effects of CO2 laser and electrocautery scalpels may also be associated with deeper staining, distorted nuclei, and thrombosed or collapsed blood vessels and lymphatics in comparison to traditional cold knife scalpels. In addition, tissue adjacent to the electrode is subject to tissue fragmentation. Though each may have its own distinct advantages for the practitioner including costs, due to the consequences of using heat, each type of scalpel has similar results in terms of the consequences for the patient. Thus, a better instrument is needed to avoid adverse effects to the patient.
A second technique for reducing bleeding in surgery is through topical hemostatic agents. Hemostatic agents come in a variety forms including liquid, foam, sponge, mesh and powder that can be applied by the surgeon at the site of incision. These types of topical agents are made from human pooled proteins, including thrombin and fibrin. Topical agents initiate the blood clotting and coagulation cascade; however they can have side effects due to their active ingredients. Topical agents such as INSTAT [Ethicon], GELFOAM [Pfizer] and SURGICEL [Ethicon] can respectively cause allergic reactions, infection, adhesions, and foreign body reactions. Additionally, particularly for larger vessels this method is not effective alone. Pressure must be applied to large vessels before using this method. Thus, alternative blood loss prevention methods could decrease the associated risks of foreign blood products.
While these current methods are effective for lessening blood loss as compared to cold knife scalpels, there has been little investigation into creating catalytic binding sites on the scalpel surface to catalyze the body's natural coagulation as an alternative to the damaging effects of heat. Thus, a need exists for a less damaging cutting device than those currently known in the art. Beneficially, such a device may also control bleeding, minimize pain, discourage infection, promote healing, and/or provide other benefits.
Some medical devices reside temporarily or permanently in the body of a patient. These devices include catheters and implantable medical devices (artificial organs, cardiac-assist devices, artificial joints, deep brain stimulation or DBS, etc.). Beneficially, a surface material for these devices could minimize microbial growth and blood clotting and also maximize biocompatibility to minimize the body's immune response to the implant and yet allow healing and/or provide other benefits.
Current approaches for catheters and implantable devices include attaching molecules to the surface to create a molecule-thick coating. For example, perfluorocarbon has been used as a molecular coating to create a universally repellant surface for blood clots and biofilms. Additional technologies coat device surfaces with gold, silver, and selenium nanoparticles to give them antimicrobial properties. However, current device surface coating technologies often cannot incorporate all desirable aspects, such as antimicrobial and immunosuppressant action and promotion of healing. Thus, a need exists for a device incorporating the action of a mixture of molecules with multiple complementary functions benign to the body's own responses.